Flexible method for producing oil bases and distillates from feedstock containing heteroatoms

ABSTRACT

The present invention concerns an improved procedure for producing basic oils and in particular very high quality oils, i.e. oils possessing a high viscosity index (VI), a low aromatics content, good UV stability and a low pour point, from oil cuts having an initial boiling point higher than 340° C., possibly with simultaneous production of middle distillates (in particular gasoils and kerosene) of very high quality, i.e. having a low aromatics content and a low pour point.  
     More precisely, the invention concerns a flexible procedure for producing basic oils and middle distillates from a charge containing heteroatoms, i.e. containing more than 200 ppm by weight of nitrogen, and more than 500 ppm by weight of sulphur. The procedure comprises at least one hydrorefining stage, at least one stage of catalytic dewaxing on zeolite, and at least one hydrofinishing stage.

[0001] The present invention describes an improved procedure forproducing basic oils of very high quality, i.e. possessing a highviscosity index (VI), a low aromatics content, good UV stability and alow pour point, from oil cuts having an initial boiling point higherthan 340° C., possibly with simultaneous production of middledistillates (in particular gasoils and kerosene) of very high quality,i.e. having a low aromatics content and a low pour point.

[0002] More precisely, the invention concerns a flexible procedure forproducing basic oils and middle distillates from a charge containingheteroatoms (e.g. N, S, O etc. and preferably without metals), i.e.containing more than 200 ppm by weight of nitrogen, and more than 500ppm by weight of sulphur. The procedure comprises at least onehydrorefining stage, at least one stage of catalytic dewaxing onzeolite, and at least one hydrofinishing stage.

PRIOR ART

[0003] The U.S. Pat. No. 5,976,354 describes a procedure for producingoils comprising these three stages.

[0004] The first stage involves the denitrogenization and desulphurationof the charge in the presence of a non-noble metal-based catalyst ofGroups VIII and/or VI B and an alumina or silica-alumina support, thepreferred catalysts being prepared by impregnation of the preformedsupport.

[0005] The effluent obtained, after stripping of the gases, is treatedin the catalytic dewaxing stage on a zeolite ZSM-5 or ZSM-35-basedcatalyst, or SAPO-type molecular sieve, the catalyst also containing atleast one hydrogenating catalytic metal. The procedure ends with ahydrofinishing stage to achieve saturation of the aromatics using acatalyst comprising Pt and Pd oxides on alumina, or else using apreferred catalyst based on zeolite Y.

[0006] In a communication of D. V. Law at the 7th Refinery TechnologyMeeting in Bombay, 6-8 December 1993, a procedure for production of oilsand middle distillates is described.

[0007] It comprises a first hydrocracking stage achievingdenitrogenization, cracking of the low-VI (viscosity index) componentsand a rearrangement (aromatics saturation, opening of naphthenic cycle)producing high-VI compounds.

[0008] This stage is carried out in the presence of a cogel-typecatalyst having a uniform strong dispersion of a hydrogenating elementand a single pore-size distribution. Such catalysts are reputedlyclearly superior to catalysts obtained by impregnation of the support.The catalyst ICR106 is an example. The effluent obtained is distilled,the naphtha, jet fuel and diesel cuts are separated, as are the gases,and the remaining fractions (neutral oils and bright stock) are treatedby catalytic dewaxing.

[0009] During this stage, isomerization of the n-paraffins is carriedout on an ICR404 catalyst. The process also ends with a hydrofinishingstage.

[0010] No information is provided concerning the use of the dewaxing andhydrofinishing stages. It is indicated that the VI of the final oilincreases according to the wax content of the charge and the severity ofthe hydrocracking process.

OBJECT OF THE INVENTION

[0011] The applicant has focussed its research efforts on providing animproved procedure for manufacturing lubricating oils and very highquality oils in particular.

[0012] This invention thus relates to a series of procedures for thejoint production of basic oils and middle distillates (in particulargasoils) of very high quality, from oil cuts with an initial boilingpoint above 340° C. The oils obtained have a high viscosity index VI, alow aromatics content, low volatility, good UV stability and a low pourpoint.

[0013] The present application proposes an alternative procedure to theprocedures of the prior art which, by a particular choice of catalystsand conditions, makes it possible to produce good-quality oils andmiddle distillates, under mild conditions and with long cycle durations.

[0014] In particular, and unlike the usual series of procedures or thosefrom the prior state of the art, this procedure is not limited in thequality of the oil products that it makes it possible to obtain; inparticular a judicious choice of operating conditions makes it possibleto obtain medicinal white oils (i.e. oils of excellent quality).

[0015] More precisely, the invention concerns a procedure for productionof oils and middle distillates from a charge containing more than 200ppm by weight of nitrogen, and more than 500 ppm by weight of sulphur,of which at least 20% boils above 340° C., comprising the followingstages:

[0016] (a) hydrorefining of the charge, carried out at a temperature of330°-450° C., under a pressure of 5-25 MPa, at a spatial velocity of0.1-10 h⁻¹, in the presence of hydrogen in a hydrogen/hydrocarbon volumeratio of 100:200, and in the presence of an amorphous catalystcomprising a support and at least one non-noble metal of Group VIII, atleast one metal of Group VI B, and at least one doping element chosenfrom the group formed by phosphorus, boron and silicon.

[0017] (b) from the effluent obtained in stage (1), separation of atleast the gases and compounds with a boiling point below 150° C.,

[0018] (c) catalytic dewaxing of at least part of the effluent producedin stage (b) which contains compounds with a boiling point above 340°C., carried out at a temperature of 200-500° C., under a total pressureof 1-25 MPa, at an hourly volume rate of 0.05-50 h⁻¹, with 50-2000 l ofhydrogen/l of charge, and in the presence of a catalyst comprising atleast one hydro-dehydrogenating element and at least one molecularsieve,

[0019] (d) hydrofinishing of at least part of the effluent produced instage (c), carried out at a temperature of 180-400° C., under a pressureof 1-25 MPa, at a volume-time rate of 0.05-100 h⁻¹, with 50-2000 l ofhydrogen/l of charge, and in the presence of an amorphous catalyst forhydrogenation of the aromatics, comprising at least onehydro-dehydrogenating metal and at least one halogen.

[0020] (e) separation of the effluent obtained in stage (d) to obtain atleast one oil fraction.

[0021] Generally, the effluent produced by the hydrofinishing treatmentis subjected to a distillation stage comprising atmospheric distillationand vacuum distillation, in order to separate at least one oil fractionwith an initial boiling point above 340° C., and which preferably has apour point below −10° C., a content by weight of aromatics compoundsbelow 2%, and a VI above 95, a viscosity at 100° C. of at least 3 cSt(i.e. 3 mm²/s) and in order possibly to separate at least one preferredmedium distillate fraction, having a pour point below or equal to −10°C. and preferably −20° C., an aromatics content of at least 2% by weightand a polyaromatics content of 1% by weight maximum.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The procedure according to the invention comprises the followingstages:

[0023] Stage (a): Hydrorefining

[0024] The hydrocarbonated charge from which the high-quality oils andpossibly middle distillates are obtained contains at least 20% by volumeboiling above 340° C.

[0025] Widely varying charges can therefore be treated by thisprocedure.

[0026] The charge can, for example, be vacuum distillates produced bydirect distillation of the crude or of conversion units such as FCC,coker or visco-reduction, or, resulting from desulphuration orhydroconversion of ATRs (atmospheric residues) and/or of VRs (vacuumresidues), or hydrocracking residues, or else the charge can be ade-asphalted oil, or any mixture of the above-mentioned charges. Theabove list is not exhaustive. In general, the charges suitable for theoils aimed at have an initial boiling point above 340° C., and, evenbetter, above 370° C.

[0027] The nitrogen content of the charge is generally greater than 200ppm by weight, preferably greater than 400 ppm by weight and still morepreferably greater than 500 ppm by weight.

[0028] The sulphur content of the charge is generally greater than 500ppm and most often greater than 1% by weight.

[0029] The charge, which may comprise a mixture of the abovementionedcharges, is initially subjected to a hydrorefining process, during whichit is brought into contact, in the presence of hydrogen, with at leastone catalyst comprising an amorphous support and at least one metalhaving a hydro-dehydrogenating function provided, for example, by atleast one element of Group VI B and at least one element of Group VIII,at a temperature between 330 and 450° C., preferably 360-420° C., undera pressure between 5 and 25 MPa, preferably below 20 MPa, its spatialvelocity being between 0.1 and 10 h⁻¹ and advantageously between 0.1 and6 h⁻¹, preferably between 0.3-3 h⁻¹, and the quantity of hydrogenintroduced is such that the hydrogen/hydrocarbon volume ratio is between100 and 2000.

[0030] During the first stage, the use of a catalyst promotinghydrogenation in relation to cracking, used under appropriatethermodynamic and kinetic conditions, allows a considerable reduction inthe content of condensed polycyclic aromatic hydrocarbons. Under theseconditions, the greater part of the nitrogenated and sulphuratedproducts of the charge are also transformed. This operation thus makesit possible to largely eliminate two types of compounds: the aromaticcompounds and the organic nitrogenated compounds initially present inthe charge.

[0031] Taking account the presence of organic sulphur and nitrogenpresent in the

[0032] charge, the stage (a) catalyst will function in the presence ofsignificant quantities of NH₃ and H₂S respectively resulting from thehydro-denitrogenation and hydro-desulphuration of the organicnitrogenated and organic sulphurated compounds present in the charge.

[0033] In this first stage which involves hydro-denitrogenation,hydro-desulphuration, hydrogenation of the aromatics and cracking of thecharge to be treated, the charge is purified whilst simultaneouslyallowing the properties of the basic oil leaving this first stage to beadjusted with reference to the quality of the basic oil which is to beobtained from this procedure. Advantageously, this regulation can becarried out by taking advantage of the nature and quality of thecatalyst used in the first stage and/or the temperature of this firststage, in order to enhance the cracking and hence the viscosity index ofthe basic oil. If we consider the fraction with an initial boiling pointabove 340° C. (or even 370° C.), at the end of this stage, its viscosityindex obtained after dewaxing using solvent (methyl-isobutyl ketone) atapprox. −20° C. is preferably between 80 and 150, or, better, between 90and 140, even 90 and 135. To obtain such indices, in general theconversion of the charge into cracked products, at boiling points below340° C. (or even 370° C.), is equal to approximately 60% by weightmaximum, or even 50% by weight maximum.

[0034] The support is generally based on (or preferably essentially madeup of) alumina or amorphous silica-alumina; it can also contain boronoxide, magnesia, zirconia, titanium oxide, or a combination of theseoxides. The support is preferably acid. The hydro-dehydrogenatingfunction is preferably achieved by at least one metal or metal compoundof Groups VIII and VI preferably chosen from molybdenum, tungsten,nickel and cobalt.

[0035] This catalyst can advantageously contain at least one elementincluded in the group formed by the elements phosphorus, boron andsilicon.

[0036] The preferred catalysts are the catalysts NiMo and/or NiW andalso the catalysts NiMo and/or NiW on alumina doped with at least oneelement contained in the group of atoms formed by phosphorus, boron andsilicon, or else the catalysts NiMo and/or NiW on silica-alumina, or onsilica-alumina oxide of titanium doped with at least one elementcontained in the group of atoms formed by phosphorus, boron and silicon.

[0037] The still more preferred catalysts are those containingphosphorus, those containing phosphorus and boron, those containingphosphorus, boron and silicon, and those containing boron and silicon.The catalysts which are suitable for use of the procedure according tothe invention can also advantageously contain at least one element ofGroup V B (for example niobium) and/or at least one element of Group VIIA (for example fluorine) and/or at least one element of Group VII B (forexample rhenium, manganese).

[0038] Phosphorus, boron and silicon are preferably introduced asaccelerator elements.

[0039] The accelerator element and, in particular, the siliconintroduced onto the support according to the invention, is mainlylocated on the support matrix and perhaps characterized by techniquessuch as the Castaing microprobe (distribution profile of the variouselements), electron microscopy by transmission in conjunction with Xanalysis of the catalyst components, or else by establishing adistribution cartography of the elements present in the catalyst byelectronic microprobe. These local analyses will provide the location ofthe various elements, in particular the location of the acceleratorelement, in particular the location of the amorphous silicon due to theintroduction of the silicon onto the support matrix. The location of thesilicon in the structure of the zeolite contained in the support is alsorevealed. Moreover, a quantitative estimate of the local contents ofsilicon and other elements may be carried out.

[0040] On the other hand the RMN of the ²⁹Si solid on rotation to themagic angle is a technique that makes it possible to detect the presenceof amorphous silicon introduced into the catalyst.

[0041] The total concentration of oxides of metals of Groups VIB (W, Mobeing preferred) and VIII (Co, Ni being preferred) is between 1 and 40%,or even 5 and 40% by weight and preferably between 7 and 30%, and theweight ratio expressed in metal oxide between metal (or metals) of GroupVIB on metal (or metals of Group VIII is preferably between 20 and 1.25and still more preferably between 10 and 2. The catalyst's content ofdoping element is at least 0.1% by weight and below 60%. The catalyst'sphosphorus (oxide) content is generally 20% by weight maximum,preferably 0.1-15%, the boron (oxide) content is generally 20% by weightmaximum, preferably 0.1-15%, and the silicon content (oxide and outsidematrix) is generally 20% by weight maximum, and preferably 0.1-15%.

[0042] The catalyst's content of an element of Group VII A is at themost 20% by weight, preferably 0.1-15%, whilst the content of an elementof Group VII B is at the most 50% by weight, preferably 0.01-30% and thecontent of an element of Group V B at the most 60% by weight, andpreferably 0.140%.

[0043] Thus the advantageous catalysts according to the inventioncontain at least one element chosen from Co and Ni, at least one elementchosen from Mo and W, and at least one doping element chosen from P, Band Si, said elements being deposited on a support.

[0044] Other preferred catalysts contain phosphorus and boron as dopingelements, deposited on an alumina-based support.

[0045] Other preferred catalysts contain boron and silicon as dopingelements, deposited on an alumina-based support.

[0046] Other preferred catalysts also contain phosphorus in addition toboron and/or silicon.

[0047] All these catalysts preferably contain at least one element ofGroup VIII chosen from Co and Ni, and at least one element of Group VIBchosen from W and Mo.

[0048] Stage (B): Stage of Separation of the Products Formed

[0049] The effluent resulting from this first stage is conveyed (stageb) to a separation train comprising a means of separating the gases (forexample a gas-liquid separator) making it possible to separate gasessuch as the hydrogen, hydrogen sulphide (H₂S), and ammonia (NH₃) formed,as well as gaseous hydrocarbons with up to 4 carbon atoms. Then at leastone effluent containing products with a boiling point higher than 340°C. is recovered.

[0050] Following gas-liquid separation, the effluent undergoesseparation of the compounds with a boiling point below 150° C.(gasoline) generally achieved by stripping and/or atmosphericdistillation.

[0051] The separation stage (b) preferably ends with vacuumdistillation.

[0052] The separation train can thus be achieved in different ways.

[0053] It may for example include a stripper to separate the gasolineformed during stage (a) and the resulting effluent is conveyed into avacuum distillation column to recover at least one oil fraction and alsomiddle distillates.

[0054] In another version, the separation train can include, before thevacuum distillation, atmospheric distillation of the effluent producedby the separator or stripper.

[0055] During the atmospheric distillation, at least one mediumdistillate fraction is recovered. At least one gasoline fraction isobtained in the stripper or during atmospheric distillation. Theatmospheric distillation residue is then passed to the vacuumdistillation section.

[0056] The vacuum distillation makes it possible to obtain a fraction orfractions of oils of different grades depending on the operator'srequirements.

[0057] Thus at least one fraction of oil is obtained with an initialboiling point above 340° C., or, better, above 370° C., or 380° C., or400° C.

[0058] This fraction, after dewaxing with solvent (methyl-isobutylketone) at approx. −20° C., has a VI of at least 80, and generallybetween 80 and 150 or, better, between 90 and 140 or even 90 and 135.

[0059] According to the invention, this fraction (residue) will then betreated alone or in a mixture with one or more other fractions in thecatalytic dewaxing stage.

[0060] Stage (a) thus leads to the production of compounds with lowerboiling points which can advantageously be recovered during theseparation stage (b). They include at

[0061] least one gasoline fraction and at least one medium distillatefraction (for example 150-380° C.) which generally has a pour pointbelow −20° C. and a cetane number above 48.

[0062] In another version geared more towards the production of mediumdistillate with a very low pour point, the cutting point is lowered,and, for example, instead of cutting at 340° C., gas oils and possiblykerosenes can for example be included in the fraction containing thecompounds boiling above 340° C. For example, a fraction with an initialboiling point of at least 150° C. is obtained. This fraction will thenbe passed to the dewaxing section.

[0063] Generally, in this text the term “middle distillates” refers tothe fraction(s) with an initial boiling point of at least 150° C. andfinal boiling point up to just before that of the oil (the residue),i.e. generally up to 340° C., or preferably approximately 380° C.

[0064] Stage (c): Catalytic Hydrodewaxing (CHDW)

[0065] At least one fraction containing the compounds boiling above 340°C., as defined above, resulting from stage (b) is then subjected, aloneor in mixture with other fractions resulting from the resulting from thesequence of stages (a) and (b) of the procedure according to theinvention, to a catalytic dewaxing stage in the presence of hydrogen anda hydrodewaxing catalyst comprising an acid function and ahydro-dehydrogenating metallic function and at least one matrix.

[0066] It should be noted that the compounds boiling above 340° C. arepreferably always subjected to catalytic dewaxing, whatever the methodof separation chosen in stage (b).

[0067] The acid function is provided by at least one molecular sievewhose microporous system has at least one main type of channel whoseopenings are formed from rings containing 10 or 9 T atoms. The T atomsare tetrahedral atoms making up the molecular sieve and can be at leastone of the elements contained in the group following the atoms (Si, Al,P, B, Ti, Fe, Ga). In the rings forming the channel openings, the Tatoms, defined above, alternate with an equal number of oxygen atoms.Thus to say that the openings are formed from rings containing 10 or 9oxygen atoms is equivalent to saying that they are formed from ringscontaining 10 or 9 T atoms.

[0068] The molecular sieve used to make up the hydrodewaxing catalystcan also comprise other types of channels, whose openings are formedfrom rings containing less than 10 T atoms or oxygen atoms.

[0069] The molecular sieve used to make up the catalyst also has abridge width, i.e. the distance between two pore openings, as definedabove, which is no greater than 0.75 nm (1 nm=10⁻⁹ m), preferablybetween 0.50 nm and 0.75 nm, and still more preferably between 0.52 nmand 0.73 nm.

[0070] The bridge width is measured by using a graphic and molecularmodelling tool such as Hyperchem or Biosym, which makes it possible toconstruct the surface of the molecular sieves in question and, takingaccount the ion rays of the elements present in the sieve structure, tomeasure the bridge width.

[0071] The catalyst suitable for this procedure is characterized by acatalytic test known as a standard pure n-decane transformation testwhich is carried out under partial pressure of 450 kPa of hydrogen andpartial pressure of n-C₁₀ of 1.2 kPa, i.e. a total pressure of 451.2 kPain a fixed bed and with a constant n-C₁₀ rate of flow of 9.5 ml/h, atotal rate of flow of 3.6 l/h and a catalyst mass of 0.2 g. The reactionis carried out in a descending flow. The rate of conversion iscontrolled by the temperature at which the reaction takes place. Thecatalyst subjected to said test is made up of pure pelletized zeoliteand 0.5% by weight of platinum.

[0072] The n-decane, in the presence of the molecular sieve and ahydro-dehydrogenating function, will undergo hydroisomerizationreactions which will produce isomerized products with 10 carbon atoms,and hydrocracking reactions leading to the formation of productscontaining less than 10 carbon atoms.

[0073] Under these conditions a molecular sieve used in thehydrodewaxing stage according to the invention must have thephysicochemical characteristics described above and lead, for a yield ofn-C₁₀ isomerized products in the region of 5% by weight (the rate ofconversion is controlled by the temperature), to a 2-methylnonane/5-methyl nonane ratio greater than 5 and preferably greater than7.

[0074] The use of molecular sieves thus selected, under the conditionsdescribed above, from the numerous molecular sieves already existing,makes it possible in particular to produce products with a low pourpoint and high viscosity index with good yields within the framework ofthe procedure according to the invention.

[0075] The molecular sieves that can be used to make up the catalytichydrodewaxing catalyst are, for example, the following zeolites:Ferrierite, NU-10, EU-13, ZSM-48 and zeolites of the same structuraltype.

[0076] The molecular sieves used to make up the hydrodewaxing catalystare preferably contained within the group formed by ferrierite and thezeolite EU-1.

[0077] The content by weight of the molecular sieve in the hydrodewaxingcatalyst is between 1 and 90%, preferably between 5 and 90% and stillmore preferably between 10 and 85%.

[0078] The matrices used for formation of the catalyst include theexamples in the following list, which is not exhaustive: alumina gels,aluminas, magnesia, amorphous silica-aluminas, and mixtures of these.Techniques such as extrusion, pelletization or bowl granulation can beused to carry out the formation operation.

[0079] The catalyst also includes a hydro-dehydrogenation function,provided, for example, by at least one element of Group VII andpreferably at least one element included in the group formed by platinumand palladium.

[0080] The content by weight of non-noble metal of Group VIII, inrelation to the final catalyst, is between 1 and 40%, preferably between10 and 30%. In this case, the non-noble metal is often associated withat least one metal of Group VIB (Mo and W being preferred). If there isat least one noble metal of Group VIII, the content by weight, inrelation to the final catalyst, is below 5%, preferably below 3% andstill more preferably below 1.5%.

[0081] In the case of utilization of noble metals of Group VIII, theplatinum and/or palladium are preferably located on the matrix, definedas above.

[0082] The hydrodewaxing catalyst according to the invention can,moreover, contain 0 to 20%, preferably 0 to 10% by weight (expressed inoxides) of phosphorus. The combination of metal(s) of Group VI B and/ormetal(s) of Group VIII with phosphorus is particularly advantageous.

[0083] If we consider the fraction of the effluent with a boiling pointabove 340° C. which can be obtained at the end of stages (a) and (b) ofthe procedure according to the invention, and which is to be treated inthis hydrodewaxing stage (c), it has the following characteristics: aninitial boiling point above 340° C. and preferably above 370° C., a pourpoint of at least 15° C., a nitrogen content below 10 ppm by weight, asulphur content below 50 ppm by weight, preferably below 20 ppm, or evenbetter, below 10 ppm by weight, a viscosity index obtained afterdewaxing with solvent (methyl isobutyl ketone) at approximately −20° C.,which is at least equal to 80, preferably between 80 and 150, and,better, between 90 and 140 or even 90 and 135, an aromatics compoundscontent below 15% and preferably below 10% by weight, a viscosity at100° C. above or equal to 3 cSt (mm²/s).

[0084] The operating conditions under which the hydrodewaxing stage ofthe procedure according to the invention takes place are as follows:

[0085] the reaction temperature is between 200 and 500° C., preferablybetween 250 and 470° C., and advantageously 270-430° C.;

[0086] the pressure is between 0.1 (or 0.2) and 25 MPa (106 Pa) andpreferably between 0.5 (1.0) and 20 MPa;

[0087] the hourly volume rate (hvr expressed as the volume of chargeinjected per catalyst volume unit and per hour) is between approximately0.05 and approximately 50 and preferably between approximately 0.1 andapproximately 20 h⁻¹ and, still more preferably, between 0.2 and 10 h⁻¹.

[0088] These are chosen so as to obtain the desired pour point.

[0089] Contact between the charge entering the dewaxing section and thecatalyst takes place in the presence of hydrogen. The rate of hydrogenused and expressed in litres of hydrogen per litre of charge is between50 and approximately 2000 litres of hydrogen per litre of charge, andpreferably between 100 and 1500 litres of hydrogen per litre of charge.

[0090] Stage (d): Hydrofinishing

[0091] The effluent from the catalytic hydrodewaxing stage, preferablyin its entirety and without intermediate distillation, is passed to ahydrofinishing catalyst in the presence of hydrogen, in order to achieveaccelerated hydrogenation of the aromatic compounds which aredetrimental to the stability of oils and distillates. However theacidity of the catalyst must be sufficiently low not to lead to too muchformation of cracked products with a boiling point below 340° C., so asnot to degrade the final yields of oils in particular.

[0092] The catalyst used in this stage comprises at least one metal ofGroup VIII and/or at least one element of Group VIB of the periodictable. Strong metallic functions: platinum and/or palladium, ornickel-tungsten, or nickel-molybdenum combinations will beadvantageously used to achieve accelerated hydrogenation of thearomatics.

[0093] These metals are deposited and dispersed on a support of thecrystalline or amorphous oxide type, such as for example, aluminas,silicas, silica-aluminas. The support contains no zeolite.

[0094] The hydrofinishing (HDF) catalyst can also contain at least oneelement of Group VII A of the periodic table of the elements. Thesecatalysts preferably contain fluorine and/or chlorine.

[0095] The contents by weight of metals are between 10 and 30% in thecase of non-noble metals and below 2%, preferably between 0.1 and 1.5%,and still more preferably between 0.1 and 1.0% in the case of the noblemetals.

[0096] The total quantity of halogen is between 0.02 and 30% by weight,advantageously within the range 0.01 to 15%, or 0.01 to 10%, orpreferably 0.01 to 5%.

[0097] Among the catalysts that can be used in this HDF stage, leadingto excellent performances, in particular to obtain medicinal oils,mention may be made of catalysts containing at least one noble metal ofGroup VIII (platinum for example) and at least one halogen (chorineand/or fluorine), a combination of chlorine and fluorine beingpreferred. A preferred catalyst is made up of noble metal, chlorine,fluorine and alumina.

[0098] The operating conditions under which the hydrofinishing stage ofthe procedure according to the invention takes place are as follows:

[0099] the reaction temperature is between 180 and 400° C., preferablybetween 210 and 350° C., and advantageously 220-320° C.;

[0100] the pressure is between 0.1 and 25 MPa (10⁶ Pa) and preferablybetween 1.0 and 20 MPa;

[0101] the hourly volume rate (hvr expressed as the volume of chargeinjected per catalyst volume unit and per hour) is between approximately0.05 and approximately 100 and preferably between approximately 0.1 andapproximately 30 h⁻¹.

[0102] Contact between the charge and the catalyst takes place in thepresence of hydrogen. The rate of hydrogen used and expressed in litresof hydrogen per litre of charge is between 50 and approximately 2000litres of hydrogen per litre of charge, and preferably between 100 and1500 litres of hydrogen per litre of charge.

[0103] Generally the temperature of the HDF stage is lower than thetemperature of the catalytic hydrodewaxing (CHDW) stage. The differencebetween T_(CHDW) and T_(HDF) is generally between 20 and 200 andpreferably between 30 and 100° C.

[0104] Stage (e): Separation

[0105] The effluent from the HDF stage is passed into a separation ordistillation train, which includes separation of the gases (for exampleby means of a gas-liquid separator) making it possible to separate fromthe liquid products, gases such as hydrogen and gaseous hydrocarbonscomprising 1-4 carbon atoms. This separation train can also includeseparation of the compounds with a boiling point below 150° C.(gasoline) formed during the previous stages (for example strippingand/or atmospheric distillation). Separation stage (a) ends with avacuum distillation process to recover at least one oil fraction. Themiddle distillates formed during the previous stages are also recoveredduring separation in stage (e).

[0106] The separation train can be achieved in different ways.

[0107] It may for example comprise a stripper to separate the gasolineformed during stage (a) and the resulting effluent is passed into avacuum distillation column to recover at least one oil fraction and alsomiddle distillates.

[0108] In another version, the separation train may include, before thevacuum distillation section, a section for atmospheric distillation ofthe effluent from the separator or stripper.

[0109] In the atmospheric distillation section, at least one mediumdistillate fraction is recovered (these are the distillates formedduring the previous stages). At least one gasoline fraction is obtainedin the stripper or the atmospheric distillation section. The atmosphericdistillation residue is passed to the vacuum distillation section.

[0110] The vacuum distillation makes it possible to obtain the oilfraction or fractions of different grades depending on the requirementsof the operator.

[0111] All the combinations are possible, the cutpoints being adjustedby the operator on the basis of his requirements (product specificationsfor example).

[0112] This separation also makes it possible to improve thecharacteristics of the oil fraction, such as for example NOACK andviscosity, by choosing the cutpoint between gasoil and the oil fraction.

[0113] The basic oils obtained according to this procedure most oftenhave a pour point below 10° C., a content by weight of aromaticcompounds below 2%, an IV above 95, preferably above 105 and still morepreferably above 120, a viscosity of at least 3.0 cST at 100° C., anASTM D1500 colour below 1, and preferably below 0.5, and UV stabilitysuch that the ASTM D1500 colour increase is between 0 and 4, andpreferably between 0.5 and 2.5.

[0114] The UV stability test, adapted from the ASTM D925-55 and D1148-55procedures, provides a quick method for comparing the stability oflubricating oils exposed to a source of ultraviolet rays. The testchamber is made up of a metal enclosure with a turning plate on whichthe oil samples are placed. A bulb producing the same ultraviolet raysas those of sunlight, and positioned at the top of the test chamber, isdirected downwards onto the samples. The samples include a standard oilwith known UV characteristics. The ASTM D1500 colour of the samples isdetermined at t=0, then after 45 hours of exposure at 55° C. The resultsare transcribed for the standard sample and the test samples as follows:

[0115] a) initial ASTM D 1500 colour,

[0116] b) final ASTM D1500 colour,

[0117] c) increase in colour,

[0118] d) cloudy,

[0119] e) precipitate.

[0120] Another advantage of the procedure according to the invention isthat it also makes it possible to obtain medicinal white oils. Medicinalwhite oils are mineral oils obtained by accelerated refining of oil,their quality is subject to various regulations aimed at guaranteeingtheir harmlessness for pharmaceutical applications, they are non-toxicand are characterized by their density and viscosity. Medicinal whiteoils are essentially made up of saturated hydrocarbons, they arechemically inert and have a low aromatic hydrocarbons content.Particular attention is paid to aromatic compounds and in particular to6 polycyclic aromatic hydrocarbons (P.A.H.) which

[0121] are toxic and present in concentrations of one part per billionby weight of aromatic compounds in the white oil. Control of the totalaromatics content can be carried out by the method ASTM D 2008; this UVadsorption test at 275, 292 and 300 nanometres makes it possible toregulate absorbency below 0.8, 0.4 and 0.3 respectively. These measuresare effected with concentrations of 1 g of oil per litre, in a 1 cmcontainer. Commercial white oils are differentiated by their viscositybut also by their original crude, which may be paraffinic or napthenic;these two parameters will lead to differences in both thephysicochemical properties of the white oils under consideration, andalso their chemical composition. Currently oil cuts, whether originatingfrom direct distillation of a crude oil followed by extraction of thearomatic compounds by a solvent, or resulting from the catalytichydrorefining or hydrocracking process, still contain significantquantities of aromatic compounds. Under the current legislation of mostindustrialized countries, “medicinal” white oils must have an aromaticscontent below a threshold imposed by the law of each of these countries.The absence of these aromatic compounds from the oil cuts is shown by aSaybolt colour specification which must be clearly at least 30 (+30), amaximum UV adsorption specification which must be below 1.60 to 275 nmon a pure product in a 1 centimetre container and a maximumspecification for absorption of DMSO extraction products which must bebelow 0.1 for the American market (Food and Drug Administration Standardno. 1211145). This last test consists of specifically extractingpolycyclic aromatic hydrocarbons using a polar solvent, often DMSO, andchecking their content in the extract by a UV absorption measurement inthe range 260-350 nm.

[0122] In addition, the medicinal white oils must also satisfy thecarbonizable substances test (ASTM D565). This consists of heating andagitating a mixture of white oil and concentrated sulphuric acid. Aftersettling out of the phases, the acid layer must have a less intensecoloration than that of a coloured reference solution or of thatresulting from combination of two glasses coloured yellow and red.

[0123] The middle distillates resulting from the series of stages of theprocedure according to the invention have pour points below or equal to−10° C. and generally −20° C., low aromatics contents (2% by weightmaximum), polyaromatics contents (di and more) below 1% by weight, andin the case of gas oils, a cetane number greater than 50 and evengreater than 52.

[0124] Another advantage of the procedure according to the invention isthat the total pressure can be the same in all the reactors of stages(c) and (d) making it possible to work in series and thus to generatecost economies.

[0125] The present invention also relates to an installation that can beused for carrying out the procedure described above.

[0126] The installation comprises:

[0127] a hydrorefining zone (2) containing a hydrorefining catalyst andhaving at least one pipe (1) for introducing the charge to be treated.

[0128] a separation train comprising at least one means of separation ofthe gases (4) with one pipe (3) carrying the effluent produced in zone(2), said means having at least one pipe (5) for removal of the gases,at least one means (7) for separation of the compounds with a boilingpoint below 150° C., said means having at least one pipe (8) for removalof the fraction containing the compounds boiling below 150° C., and atleast one pipe (9) for removal of an effluent containing compoundsboiling at at least 150° C., said train also comprising at least onevacuum distillation column (10) for treatment of said effluent, saidcolumn having at least one pipe (11) for removal of at least one oilfraction,

[0129] a catalytic dewaxing zone (15) for treatment of at least one oilfraction, having at least one pipe (16) for removal of the dewaxedeffluent,

[0130] a hydrofinishing zone (17) for treatment of the dewaxed effluentfrom the pipe (16) and having at least one pipe (18) for removal of thehydrofinished effluent,

[0131] a final separation train comprising at least one means ofseparation of the gases (19) having at least one pipe (18) carrying thehydrofinished effluent, said means having at least one pipe (20) forremoval of the gases, at least one means (22) of separation of thecompounds with a boiling point below 150° C., said means having at leastone pipe (24) for removal of the fraction containing the compoundsboiling below 150° C., and at least one pipe (25) for removal of aneffluent containing compounds boiling at at least 150° C., said trainalso comprising at least one vacuum distillation column (26) fortreatment of said effluent, said column having at least one pipe (28)for removal of at least one oil fraction.

[0132] The description can be better followed by referring to FIG. 1.

[0133] The charge is introduced by the pipe (1) in the hydrorefiningzone (2) which comprises one or more catalytic beds of a hydrorefiningcatalyst, arranged in one or more reactors.

[0134] The effluent leaving the hydrorefining zone by the pipe (3) ispassed into a separation train. According to FIG. 1, this traincomprises a means of separation (4) to separate the light gases (H₂S,H₂, NH₂ etc. C1-C4) removed by the pipe (5).

[0135] The “degassed” effluent is carried by the pipe (6) into a meansof separation of the compounds with a boiling point below 150° C., whichis for example a stripper (7) having a pipe (8) for removal of the150-fraction and a pipe (9) to carry the stripped effluent into a vacuumdistillation column (10).

[0136] Said column makes it possible to separate at least one oilfraction removed for example by the pipe (11), and by at least one pipe(12), at least one medium distillate fraction is removed. Depending onthe requirements of the operator, the light oil fractions may possiblybe separated into different grades, removed by the pipes (13) (14) inFIG. 1.

[0137] The oil fraction obtained in the pipe (11) is passed into thecatalytic dewaxing zone (15) which comprises one or more catalytic bedsof catalytic dewaxing catalyst, arranged in one or more reactors. Theoil fractions in the pipes (13) (14) can also be passed into the zone(12), alone, or mixed with each other or with the heavier oil from thepipe (11).

[0138] The dewaxed effluent thus obtained is all removed from the zone(15) by the pipe (16). It is then treated in the hydrofinishing zone(17) which comprises one or more catalytic beds of hydrofinishingcatalyst, arranged in one or more reactors.

[0139] The hydrofinished effluent thus obtained is removed by the pipe(18) to the final separation train.

[0140] In FIG. 1, this train comprises a means of separation (19) forseparation of the light gases removed by the pipe (20).

[0141] The “degassed” effluent is carried by the pipe (21) into adistillation column. In FIG. 1, this is an atmospheric distillationcolumn (22) to separate one or more medium distillate fractions removedby, for example, a pipe (23) and possibly a gasoline fraction removed bya pipe (24).

[0142] In FIG. 1, the atmospheric distillation residue removed by thepipe (25) is carried into a vacuum distillation column (26) whichseparates one or more light oil fractions (according to the requirementsof the operator) removed by at least one pipe, for example one pipe (27)and makes it possible to recover a basic oil fraction by the pipe (28).

[0143] In FIG. 2, another method of separation is represented.

[0144] Not all the elements denoted by the reference marks will bedescribed, but only the separations.

[0145] In FIG. 2, the effluent produced in the zone (2) which has beendegassed is carried by the pipe (6) into a distillation column (30)which, here, is an atmospheric distillation column. In this column, oneor more gasoline and/or medium distillate fractions are separated andremoved by the pipes (31, (32) in FIG. 2, and the residue containing theheavy products (boiling point generally above 340° C., or even 370° C.or above) is removed by the pipe (33).

[0146] This residue is, according to FIG. 2, carried into a vacuumdistillation column (10) from which an oil fraction is separated by thepipe (11) and one or more light oils of different grades may possibly beremoved by one or more pipes (34), (35) for example, if the operatorwishes to obtain these.

[0147] In FIG. 2, the final separation train comprises a means ofseparation of gases (19) in which the hydrofinished effluent isintroduced by the pipe (18) and leaves, “degassed”, by the pipe (21).

[0148] This degassed effluent is carried into a stripper (36) having apipe (37) to remove the 150⁻ fraction and a pipe (38) by which thestripped effluent is removed. Said effluent is passed into a vacuumdistillation column (26) which makes it possible to separate one basicoil fraction by the pipe (28) and at least one lighter fraction. Here,these lighter fractions are for example light oils removed by the pipes(39) (40) and a single fraction removed by the pipe (41) and containinggasoline and middle distillates.

[0149] It will be understood that any combination of the separationtrains is possible, providing that the train comprises a means forremoving the light gases, a means for separating the 150⁻ fraction(stripper, atmospheric distillation), and a vacuum distillation sectionto separate the fraction containing products with a boiling point above340° C. (oil or basic oil fraction). Generally, the vacuum columns useddirectly after the stripper are regulated so as to separate at the topfractions with a boiling point below 340° C., or 370° C. or more (forexample 380° C.). In fact, the operator will control the cutpointsaccording to the products to be obtained and, for example, if he wishesto produce light oils.

[0150] The series plus traditional separator, atmospheric distillationcolumn and vacuum distillation column is most often used for the finalseparation train.

[0151] The combination of FIG. 1 is of particular interest with regardto the quality of the separation (and thus of the products obtained) fora very favourable cost (saving of one column)

1. Process for the production of oils and middle distillates from a charge containing more than 200 ppm by weight of nitrogen and more than 500 ppm by weight of sulphur, of which at least 20% by volume boils above 340° C., the charge is selected from the group formed by the vacuum distillates produced by direct distillation of the crude or conversion units, hydrocracking residues, vacuum distillates produced by desulphuration or hydroconversion of atmospheric residues or vacuum residues; deasphalted oils or mixtures of these, comprising the following stages: (a) hydrorefining of the charge, carried out at a temperature of 330° C.-450° C., under a pressure of 5-25 MPa, at a spatial velocity of 0.1-10 h⁻¹, in the presence of hydrogen in the hydrogen/hydrocarbon volume ratio of 100-2000, in the presence of an amorphous catalyst comprising a support, at least one non-noble metal of Group VIII and at least one metal of Group VI B, and at least one doping element selected from the group formed by phosphorus, boron and silicon, conversion being 60% by weight maximum. (b) from the effluent obtained in stage (a), separation of the gases and compounds with a boiling point below 150° C., followed by separation of the compounds with a boiling point below 150° C., (c) catalytic dewaxing of at least part of the effluent from stage (b), which contains compounds with a boiling point above 340° C., carried out at a temperature of 200-500° C., under a total pressure of 1-25 MPa, at an hourly volume rate of 0.05-50 h⁻¹, with 50-2000 l of hydrogen/l of charge, and in the presence of a catalyst comprising at least one hydro-dehydrogenating element and at least one molecular sieve. (d) hydrofinishing of at least part of the effluent from stage (c), carried out at a temperature of 180-400° C., under a pressure of 1-25 MPa, at an hourly volume rate of 0.05-100 h⁻¹, in the presence of 50-2000 l of hydrogen/l of charge, and in the presence of an amorphous catalyst, at least one hydro-dehydrogenating metal and at least one halogen. (e) separation of the effluent obtained in stage (d) to obtain at least one oil fraction.
 2. Process according to claim 1, in which the hydrorefining catalyst contains at least one element selected from Co and Ni, at least one element selected from Mo and W, and at least one doping element selected from P, B and Si, said elements being deposited on a support.
 3. Process according to either of claims 1 or 2, in which the hydrorefining catalyst contains as doping elements phosphorus and boron deposited on an alumina-based support.
 4. Process according to either of claims 1 or 2, in which the hydrorefining catalyst contains as doping elements boron and silicon deposited on an alumina-based support.
 5. Process according to Claim 4 in which the catalyst also contains phosphorus.
 6. Process according to any one of the preceding claims, in which the support of the hydrorefining catalyst is an acid support.
 7. Process according to any one of the preceding claims, in which the hydrorefining catalyst also contains at least one element selected from the group formed by the elements of Group VB, the elements of Group VIIA and the elements of Group VIIB.
 8. Process according to claim 7, in which the hydrorefining catalyst contains at least one element selected from niobium, fluorine, manganese and rhenium.
 9. Process according to any one of the preceding claims, in which the molecular sieve of stage (c) is selected from the group of zeolites formed by ferrierite, NU-10, EU-13, EU1, ZSM-48 and zeolites of the same structural type.
 10. Process according to any one of the preceding claims, in which the hydrofinishing catalyst contains at least one metal of Group VIII and/or at least one metal of Group VIB, a support without zeolite and at least one element of Group VIIA.
 11. Process according to claim 10 in which the catalyst contains platinum, chlorine and fluorine.
 12. Process according to any one of the preceding claims, in which, in the hydrorefining stage, the conversion into products with boiling points below 340° C. is equal to 50% by weight maximum.
 13. Process according to any one of the preceding claims, in which stage (b) and/or stage (e) is carried out by gas-liquid separation, then stripping followed by vacuum distillation.
 14. Process according to claim 13 in which stage (b) and/or stage (e) is carried out by gas-liquid separation, then atmospheric distillation followed by vacuum distillation.
 15. Process according to any one of the preceding claims, in which the charge is selected from the group formed by the vacuum distillates produced by direct distillation of the crude or conversion units, hydrocracking residues, vacuum distillates from desulphuration or hydroconversion of atmospheric residues or vacuum residues or mixtures of these.
 16. Installation for the production of oils and middle distillates comprising: a hydrorefining zone (2) containing a hydrorefining catalyst, and having at least one pipe (1) to introduce the charge to be treated a separation train comprising at least one means of separation of the gases (4) having a pipe (3) carrying the effluent from zone (2), said means having at least one pipe (5) for removal of the gases, at least one means (7) of separation of the compounds with a boiling point below 150° C., said means having at least one pipe (8) for removal of the fraction containing the compounds boiling below 150° C., and at least one pipe (9) for removal of an effluent containing compounds boiling at at least 150° C., said train also comprising at least one vacuum distillation column (10) for treatment of said effluent, said column having at least one pipe (11) for removal of at least one oil fraction, a catalytic dewaxing zone (15) for treatment of at least one oil fraction, and having at least one pipe (16) for removal of the dewaxed effluent, a hydrofinishing zone (17) for treatment of the dewaxed effluent from the pipe (16), and having at least one pipe (18) for removal of the hydrofinished effluent, a final separation train comprising at least one means of separation of the gases (19) having at least one pipe (18) carrying the hydrofinished effluent, said means having at least one pipe (20) for removal of the gases, at least one means (22) of separation of the compounds with a boiling point below 150° C., said means having at least one pipe (24) for removal of the fraction containing compounds boiling below 150° C., and at least one pipe (25) for removal an effluent containing compounds boiling at at least 150° C., said train also comprising at least one vacuum distillation column (26) for treatment of said effluent, said column having at least one pipe (28) for removal of at least one oil fraction.
 17. Installation according to claim 16 in which the means of separation of the gases (4) (19) is a gas-liquid separator.
 18. Installation according to either of claims 16 or 17 in which the means of separation (7) of the compounds with a boiling point below 150° C. is a stripper and the stripped effluent removed by the pipe (9) is passed into a vacuum distillation column (10), having at least one pipe (11) for removal of at least one oil fraction and at least one pipe (12) for removal of at least one medium distillate fraction.
 19. Installation according to either of claims 16 or 17 in which the means of separation (22) of the compounds with a boiling point below 150° C. is an atmospheric distillation section, having at least one pipe (23) for removal of at least one medium distillate fraction, at least one pipe (24) for removal of at least one gasoline fraction, and at least one pipe (25) for removal of the residue, said residue being passed into a vacuum distillation column (26) separating at least one oil fraction removed by at least one pipe (28). 